Fix macOS permanent black video after player collapse/expand cycles

In separate-window mode, hide() keeps the ordered-out window's SwiftUI
hierarchy alive (nilling contentViewController crashes AVKit), and its
updateNSView unconditionally re-attached the shared MPVOGLView -
stealing it into a window CoreAnimation never composites. The layer's
silent skip-render fallback then consumed every frame flag, so video
stayed black (climbing vo drops) until app restart.

- Decline stealing the shared view from a visible container into a
  non-visible one; owner-initiated transfers bypass the guard
- Only transfer to containers in visible windows or the window still
  tracked by ExpandedPlayerWindowManager; park the view otherwise and
  reclaim it when a container gains a window
- Log skip-render frame consumption (rate-limited) and track render
  health counters (draws/skips/dropped draws)
- Add a watchdog to the playback stats task that detects a stalled
  video output and re-attaches the view to a visible container
- Don't mount player layouts during zero-size layout passes

Yattee/Services/Player/MPV/MPVOGLView.swift

@@ -272,6 +272,26 @@ final class MPVOGLView: NSView {
         videoLayer?.resetFirstFrameTracking()
     }
 
+    /// Thread-safe snapshot of the layer's render-health counters.
+    func renderHealthSnapshot() -> MPVRenderHealth? {
+        videoLayer?.renderHealthSnapshot()
+    }
+
+    /// Human-readable description of where this shared view is currently
+    /// attached, for render-health diagnostics. Main thread only.
+    var attachmentDescription: String {
+        let superviewDesc: String
+        if let container = superview as? MPVContainerNSView {
+            superviewDesc = "container=\(container.shortID)"
+        } else if let superview {
+            superviewDesc = "superview=\(type(of: superview))"
+        } else {
+            superviewDesc = "superview=nil"
+        }
+        let windowDesc = window.map { "window=#\($0.windowNumber) visible=\($0.isVisible)" } ?? "window=nil"
+        return "\(superviewDesc) \(windowDesc) bounds=\(Int(bounds.width))x\(Int(bounds.height))"
+    }
+
     /// Clear the view to black.
     func clearToBlack() {
         videoLayer?.clearToBlack()